There is an extreme variety of objects which are to be photographed by color reversal films. Of such objects, some are desired to be photographed at a high shutter speed under a limited light. For example, in photographing a moving object such as in sports, a photographic picture with no blurs cannot be obtained unless the shutter is released at a high speed, i.e., unless the exposure time is shortened.
On the other hand, if the diaphragm of a camera is opened to a large extent, depth of field becomes smaller, and hence it becomes difficult to adjust the focus. Therefore, in photographing a moving object, too, a good photographic picture cannot be taken unless the diaphragm is considerably closed and a short exposure time is employed. For such purposes, light-sensitive materials with an ordinary sensitivity of 100 in ISO are insufficient in sensitivity.
Sports and other activities are in many cases conducted under indoor illumination or night illumination as well as under outdoor day light in the day time. In many cases, high speed films are used under indoor illumination or night illumination not only for sports. For such illumination, mercury lamps, fluorescent lamps, tungsten light, etc. are used alone or in combination. These lights are extremely different from day light in color temperature. In photographing under such illumination, a color temperature-converting filter is used for correcting color balance. However, such a filter is not of much practical use since there results a photographic finish with deteriorated sharpness and a high-speed shutter release cannot be employed due to reduction in light amount when such a filter is applied to a camera lens. On the other hand, when a high-speed color negative film is used in photographing under lights of various color temperature, color balance can be corrected when printing even if the difference in color temperature of the light source is not corrected by using a filter, and hence color unbalance of the printed picture is comparatively small.
However, when a color reversal film is used under such conditions, the finished photographic pictures show a large color unbalance due to lack of the above-described color correction.
Professional photographers often use their photographic pictures as originals for printing and, in such cases, they mostly employ color reversal films.
One of the extremely important photographic performance characteristics of high-speed color reversal film for day-light use is that change in color balance due to difference in exposure light source should be small, and hence it has been desired to provide color reversal films with such performance characteristic.
JP-B-49-6207 (corresponding to French Patent 2,004,376) (the term "JP-B" as used herein means an "examined Japanese patent publication") discloses a spectral sensitivity distribution for minimizing change in color balance for various photographing light sources.
However, this technique unavoidably involves deterioration of color reproducibility, and hence it has been eagerly desired to develop high-speed color reversal films undergoing less change in color balance due to differences in color temperature of the exposing light source without deterioration of color reproducibility.